The present invention relates to a hydrokinetic coupling apparatus with a lock-up clutch. In particular, it relates to a hydrokinetic coupling apparatus, including a turbine wheel which is capable of being coupled fixedly to a driven shaft and which is mounted within an impulse wheel casing, with which it is able to cooperate for the hydrokinetic transmission of a torque to the said driven shaft from a driving shaft which is able to be coupled fixedly to the said impulse wheel, the said apparatus further including a clutch device having a clutch disc, being a so-called lock-up clutch, adapted to lock or unlock an elastic coupling between the said turbine wheel and a radial wall of the said casing. This coupling consists of a set of circumferentially acting helical damping springs which are held in place in arched seatings which are fixed with respect to the said turbine wheel and which are open in an axial direction towards the said radial wall.
Such an apparatus is described for example in the Application WO93/13339 of Oct. 30, 1992; French patent application (FR-A-2 726 620) No. 94 13205 of Jan. 4, 1994 in the name of the Applicant is more particularly concerned with the lock-up clutch which, as is known, prevents any sliding movement between the impulse wheel and the turbine wheel except during starting phases, which leads to fuel economy.
In the first of the said documents, the helical damping springs are held in annular housings in the form of toroidal sectors defined by the curved peripheral edge of a sheet metal disc which is riveted on the turbine wheel, which involves relatively complicated fabrication (bending of sheet metal, forming through holes, etc.).
The object of the present invention is to simplify this technology.
To this end, a hydrokinetic coupling apparatus of the type described at the beginning hereof is characterised in that the said arched seatings are formed directly in the thickened peripheral portion of a turbine wheel made of mouldable material, the opposed radial ends of the said seatings serving as abutments for the corresponding ends of the said springs.
The said mouldable material could for example be synthetic material or aluminium.
In this way, the number of components is considerably reduced and the fabrication process is greatly simplified, while the weight of the turbine wheel is reduced. It also goes without saying that this new technology enables the same type of means as in the first of the above mentioned documents to be used if necessary, to ensure transmission of the torque between the clutch disc mentioned above and the helical springs, for example through lugs of the disc or through axially bent lugs of an intermediate disc which is driven in rotation by that disc, the said lugs being able to be put in both cases into engagement against the ends of the said helical springs.
The turbine wheel may be made entirely of a moulded material, including its hub for connection to the said driven shaft. In other words, the turbine wheel is then made entirely by moulding integrally with the hub,.and in that case, in order to avoid embedding in the aluminium or the synthetic material, the said hub preferably comprises a metallic insert in which splines are formed for coupling it in rotation with the driven shaft.
In another version, it can also be arranged that the said mouldable material is moulded in situ on a central metallic disc for connection to the said driven shaft.
In order to prevent the springs mentioned above from becoming embedded in the mouldable material, it can also be arranged that the said radial ends of the seatings and/or their external walls consist of metallic thrust pieces on which the said mouldable material is moulded.
It can further be arranged, with the same end in view, that each of the said seatings consists entirely of a metallic insert, with the mouldable material of the turbine wheel being moulded in situ on the inserts.